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Also purchase cialis 2.5 mg free shipping newest erectile dysfunction drugs, a full stomach mandates suction of gastric contents before intubation where possible cialis 2.5 mg with amex erectile dysfunction young age, and cricoid pressure during mask ventilation before intubation trusted 5 mg cialis do erectile dysfunction pumps work. The head is positioned neutral in the case of an infant, or with a small towel under the occiput in an older child, to achieve the “sniffing position” during laryngoscopy to align the axes of the pharynx, larynx, and trachea. The patient is preoxygenated with a tight fitting face mask for 3 to 5 minutes if possible, induction drugs are given, and positive pressure ventilation is instituted early and gently. Jaw thrust or oral airway are used if there is inadequate chest rise with bag and mask ventilation. With loss of consciousness and adequate muscle relaxation, the laryngoscope is inserted into the right side of the mouth, the tongue swept to the left out of the midline, and the blade advanced until the epiglottis is visualized. The blade is advanced further, into the vallecula with a curved blade, or under the epiglottis with a straight blade, the handle lifted with a gentle upward motion at a 45-degree angle to the surface of the bed, and position adjusted until the arytenoid cartilages and vocal cords are in view. Ventilation ensues gently; excessive positive pressure in combination with the cardiovascular depression often seen with induction drugs can result in cardiovascular collapse. Blood pressure, heart rate, and SpO must be followed carefully immediately after2 tracheal intubation; patients will sometimes P. In the case of a very tenuous patient, anticipation of full cardiac arrest should be made. The chest is auscultated for equal breath sounds; a chest radiograph is obtained as soon as possible after securing the tube. Other methods of estimating proper orotracheal depth of insertion include deliberately placing the tube in the right mainstem bronchus, and then auscultating the left chest during rapid hand ventilation while the tube is being withdrawn. This strategy is now almost obsolete, and is generally accepted to be the cause of significant lung injury, with both volutrauma and barotrauma occurring from shear stress in compliant lung units, and from high peak airway pressures. Inspiratory:expiratory ratios of 1:2 to 1:3 are preferred to allow adequate time for expansion of alveolar units with differing time constants for filling. Excessive inspired oxygen levels are toxic to the lungs, by causing oxidative damage through generation of oxygen-free radicals and toxic oxygen species. These strategies have reduced mortality, and morbidity, including days on the ventilator in pediatric patients with acute lung injury (209). Patients should be allowed to initiate spontaneous breaths, and to do as much of the work of breathing as they can, assisted by pressure- or volume-supported breaths: 5 to 10 cm H O added pressure or 3 to 5 mL/kg2 added volume. This is necessary to exercise the diaphragm and intercostal muscles, and will also P. Heavy sedation or muscle relaxation that prevents spontaneous breaths can lead to atrophy of these muscles and prolong time on the ventilator. A defined program of pulmonary toilet, including suctioning, inhaled bronchodilators, chest physiotherapy, and bronchoscopy for persistent areas of atelectasis are important to maintain gas exchange and allow progress toward extubation. Daily chest radiographs are indicated in most intubated patients to assess position of endotracheal tube, status of lung parenchyma including atelectasis, pulmonary edema, pleural effusion, pneumothorax, cardiomegaly, and pericardial effusion. These problems should be aggressively treated in order to shorten the period of mechanical ventilation; multiple studies document that longer duration of mechanical ventilation is associated with worse long-term morbidity and mortality (211,212). Monitoring of ventilatory volumes, pressures, and resistances, using sensors inside modern ventilators has limited utility in small pediatric patients. This is because the ventilator tubing itself has a dead space where no gas exchange occurs, and a portion of the tidal volume is absorbed in the mechanical expansion of the tubing with positive pressure ventilation, which is a significant proportion in small infants. Ventilator systems designed for adults cannot adequately compensate or measure pulmonary mechanics in small infants. A much more accurate measurement of pulmonary mechanics is acquired with infant pulmonary function monitors attached directly to the end of the endotracheal tube (214). These devices are integrated into many modern neonatal ventilators, or can be used as stand-alone monitors for intermittent assessment. To be ready to wean from the ventilator, the patient should have a mental status after reducing sedation that allows maintenance of a patent airway and protective airway reflexes. Quantitative measures for readiness for extubation in infants and children, that is, negative inspiratory force, forced vital capacity, minute ventilation, have limited utility, and clinical examination, chest radiograph, and blood gases are used to determine readiness. Particularly in small infants, whose small airways are easily traumatized and where even a limited amount of mucosal edema may narrow the subglottic airway considerably, dexamethasone, 0. Patients with prolonged mechanical ventilation from cardiac, pulmonary, and/or airway causes, in whom progress toward extubation is not being made, and where need for excessive doses of sedation are interfering with other aspects of general care, are considered for tracheostomy (218). There are no set guidelines in pediatric cardiac patients; and this is a complex undertaking that complicates future cardiac surgeries because of the proximity of the airway to the sternotomy incision and the risk of infection. Multidisciplinary decision-making is necessary, and tracheostomy should be considered a last resort in cardiac patients. Alternate Ventilation Strategies—Noninvasive Ventilation With the recognition that mechanical ventilation is a source of barotrauma, volutrauma, and infection, recent years have witnessed resurgence in popularity of noninvasive ventilation techniques, either to prevent intubation, or as an immediate postextubation therapy to prevent reintubation. Early Tracheal Extubation Besides the desirable hemodynamic advantages of negative pressure ventilation in the Fontan circulation, many centers have organized “fast-tracking” programs for early tracheal extubation after simple or even moderately complex cardiac surgery. Institutional practices vary widely, from no early extubation in any patients, to aggressively extubating all patients possible, including even small infants undergoing moderately complex surgery (223). A careful and cautious approach is recommended to avoid the situation where a patient who is unstable 6 to 12 hours after surgery from bleeding, inflammation, and hemodynamic compromise, and whose airway must be urgently reintubated. Multidisciplinary collaboration is important in any early extubation program (224). A collaborative approach was used that included neuraxial analgesia with caudal morphine and dexmedetomidine, and specific protocols for perfusion, surgery, nursing, and respiratory therapy (225). Even in traditionally complex populations such as orthotopic heart transplantation, earlier tracheal extubation is possible. Extubation failure, defined as need for mechanical ventilation after 96 hours posttransplant, occurred in 12. It is also used as a means of reducing shear forces the lung is exposed to with conventional ventilation. The mean airway pressure is generally higher than with conventional ventilation, allowing recruitment of lung units with different time constants. However, the pressure variation, including the peak pressure, is significantly lower, and this often leads to better gas exchange with lower risk of barotrauma. However, conclusive proof that this strategy improves outcomes, including days ventilated and survival, is lacking (227,228). Specialized, coordinated care has led to more standardized institutional treatment strategies of postoperative cardiac patients, and has contributed to decreases in mortality and morbidity (35,231). A multidisciplinary surgery conference greatly facilitates communication among the many disciplines caring for the patient. This is usually presented by the primary cardiologist or fellow in the intensive care unit. The key to successful preoperative planning conferences is concise, organized presentations of each patient, and a focused discussion, resulting in concrete plans. Failure to communicate handoff information accurately in a manner that is fully understood by the receiving team is a frequent cause of medical error that can adversely affect patient outcome (235,236). Reporting of inotropic support and other vasoactive therapy should be detailed, along with the results of the postoperative transesophageal echocardiography, including any residual defects (237). Anesthetic and other drug doses (antifibrinolytics, corticosteroids) are summarized, along with blood gases, cardiac rhythm and pacing, bleeding and blood product administration. Any problems are noted, along with general goals for early postoperative care, that is, early extubation.

Whether alterations in flow and oxygen delivery are contributors to these findings is somewhat inconclusive at this point in time buy cialis 5mg fast delivery erectile dysfunction at age 30. In utero hypoxia can lead to epigenetic programming with important influences on organ ontogeny generic 10mg cialis with visa erectile dysfunction the facts, structure order generic cialis online erectile dysfunction after zoloft, and function (15). Transposition of the great arteries may therefore be an ideal model to study as an example of acquired end-organ changes related to in utero alterations in oxygen delivery and not due to the presence of a primary syndrome affecting organ dysfunction. Barker proposed the notion that the fetal environment is dictated by maternal nutritional state (17) and that other extrinsic factors such as maternal stress (18) may influence life- long health status through “fetal programming” (19). At birth, neonatal serum creatinine levels reflect maternal renal function, but within 24 to 48 hours begin to reflect infant renal function. Prenatal identification or early postnatal detection with commencement of prostaglandin infusion will preserve ductal patency, however, retrograde diastolic flow through the ductus arteriosus may “steal” blood flow away from the renal arteries leading to hypoperfusion, hence creating the potential for acute renal dysfunction. With increasing frequency of fetal diagnosis and improved neonatal management strategies for maintaining systemic perfusion, the frequency of preoperative neonatal renal dysfunction is now relatively low. The Multi-Societal Database Committee for Pediatric and Congenital Heart Disease defines acute renal dysfunction as “new onset oliguria with sustained urine output less than 0. The definition of acute renal failure is the same but “…with eventual need for dialysis (including peritoneal dialysis and/or hemodialysis) or hemofiltration. This may be related to the deep reserve of functionality and robustness built into the design of the human kidney, in which a substantial decrease in glomerular filtration is necessary before changes can be seen in fluid and electrolyte homeostasis. Duration of cardiopulmonary bypass and hypothermic circulatory arrest are risk factors for renal dysfunction. Postoperative medications may be nephrotoxic, and in combination with fragile blood supply, may exert deleterious effects (23). Renal oximetry assessment through regional near-infrared spectroscopy has shown a relationship between low renal oximetry readings and peak postoperative serum creatinine levels (24). Cardiopulmonary bypass in patients with chronic cyanosis substantially increases the risk for postoperative renal dysfunction (26). Cyanosis leads to polycythemia with resulting blood hyperviscosity and may contribute to a diminished filtration fraction at the glomerular level (27). Anomalies such as esophageal fistula, small bowel atresia or stenosis, gut malrotation, or biliary atresia have their own well- defined natural histories and established therapeutic strategies. Healing following surgery for extracardiac conditions can be influenced by changes in regional perfusion and oxygen delivery. Feeding such infants with placement of nutritional material in the gut may on theoretical grounds, further increase the risk of local mesenteric ischemia. The proposed mechanism is one of mismatch between blood flow and oxygen delivery and the demand for perfusion, which may be increased during feeding. More recently, several centers have moved toward administering some degree of feeds in these neonates before surgery. Poor mesenteric perfusion after Norwood operation may be related to poor right ventricular systolic performance (pump failure), diastolic steal through a modified Blalock–Thomas–Taussig shunt, or perhaps a combination of the two affecting the mesenteric circulation. Reconstruction of the aorta results in a dramatic difference in flow kinetics in the descending aorta, which may modify the flow characteristics of delivery of blood to the mesenteric circulation. In the absence of a ventricle to propel blood into the pulmonary circuit, connection of the systemic venous return directly to the pulmonary arteries will allow passive flow into the lungs, achieving the goal of sufficient oxygenation to adequately sustain life. As the number of survivors of this strategy continues to grow, organ system dysfunction is being appreciated with increasing frequency. Survival following Fontan operation at up to 20 years after surgery is greater than 80% (40), however the likelihood of being free of any morbidity is quite low (41). It should also be noted that there is great variability in the manifestation of organ dysfunction in survivors of Fontan surgery, with some exhibiting minimal clinical symptoms, while others manifest significant complications. Factors that contribute to these outcomes have not yet been adequately delineated. Nevertheless, it is clear that the circulatory deficiency of the Fontan operation is an important contributor to multiple potential organ system dysfunctions, which are often clinically manifest in a very indolent and chronic manner (42,43,44,45) (Table 76. The physiologic ramifications of the Fontan operation and its impact on organ system function are many. Passive venous flow through the pulmonary circuit leads to impaired filling of the systemic ventricle. Absent the propelling force of a ventricle on the pulmonary side, some have theorized that the systemic ventricle exists in a chronically volume-deficient state (46). Filling capacity of the systemic ventricle may also be limited due to inherent characteristics such as altered relaxation mechanics as a consequence of the anatomical structure, or acquired hypertrophy or scarring secondary to initial palliative procedures such as an aortopulmonary shunt or pulmonary artery band (47). Stroke volume and resting cardiac output are often diminished compared to normal (48). Heart rate, an important variable contributing to cardiac output, can be low at rest with inability to increase adequately with exercise because of sinus node dysfunction. Due to the inability to transit adequate quantities of blood volume across the pulmonary circuit (49), the capacity to increase cardiac output as expected during exercise is significantly curtailed (50). The combination of venous congestion and decreased cardiac output diminishes the perfusion gradient to organ blood flow in a chronic manner. In general right-sided heart failure has been attributed to the development of hepatic dysfunction in adult forms of heart disease, however the changes seen in the Fontan population are somewhat distinct and unique, perhaps due to exposure to the stress of chronic venous hypertension at a young age. Hemodynamic instability at birth in combination with chronic cyanosis may lay the foundation for hepatic pathology, which is exacerbated by the imposition of chronic venous hypertension and congestion at time of Fontan operation. Recent focus on the liver indicates that hepatic fibrosis, to some degree, is prevalent in all survivors after Fontan operation. In patients with severe failing Fontan circulation, difficulty with drug clearance can be seen as well as hepatic encephalopathy. However, coagulation abnormalities are commonly present before and after Fontan operation (54). Whether this is due to mild synthetic deficiency or possible low-level enteric protein loss, or both, is unclear. The gradient (pressure differential) between the portal and systemic venous systems may be low, hence there is often little impetus for development of venous collaterals to a lower pressure system (as there is no low-pressure venous system). Platelet counts are usually on the lower end of normal (100,000–200,000) reflecting an element of splenic consumption in light of hepatic fibrotic changes. Laboratory abnormalities and fibrotic changes have been associated with low cardiac index and time from Fontan operation (58,59). She is asymptomatic with good exercise capacity and acceptable hemodynamics (pulmonary artery pressure = 10 mm Hg, no anatomical obstructions, good ventricular function). The histopathologic pattern of fibrosis differs from that seen in the most common form of hepatic scarring, that due to chronic hepatitis C infection. After Fontan, sinusoidal (central) fibrosis as well as portal fibrosis are quite common (Fig. Staging systems for hepatic fibrosis exist, but these are somewhat deficient when it comes to the Fontan pathophysiology. A staging system devised for one particular liver disease such as hepatitis C may not apply to another such as after Fontan operation (62).

The difﬁculties encountered with cloned animals described above should serve as a warning to anyone considering the procedure buy cialis with american express erectile dysfunction without pills. The temptation to replace a dead or dying child with an ‘exact copy’ may be more than some parents can bear cheap cialis 5 mg fast delivery erectile dysfunction doctor boca raton, but the potentially disastrous consequences should not be underestimated purchase cialis 10mg on-line impotence treatment options. Chromosome replication is bidirectional, which means that replication begins at a replication origin and simultaneously moves out in both directions from the replica- tion origin. Chromosome replication begins at speciﬁc nucleotide sequences located throughout the chromosome called replication origins. The stability of the replication fork is maintained by single-stranded binding proteins. Dna A protein recognizes the replication origin and opens up the double helix at that site forming a replication bubble. Type I topoisomerase introduces negative supercoiling (or relaxes positive su- percoiling). The chemotherapy drugs irinotecan and topotecan inhibit Type I topoisomerase in cancer cells. Reverse gyrase is a variant of Type I topoisomerase found in hyperthermophilic bacteria. If the 5 end of the lagging strand is not lengthened, a chromosome would get progressively shorter as the cell goes through a number of cell divisions. If the U is not corrected back to a C, then upon replication instead of the occurrence of a correct C-G base pairing, a U-A base pair- ing will occur. Clinical features include: ionizing radiation hypersensitivity; cerebellar ataxia with depletion of Purkinje cells; progressive nystagmus; slurred speech; oculocu- taneous telangiectasia (permanent dilation of preexisting small blood vessels cre- ating focal red lesions) initially in the bulbar conjunctiva followed by ear, eyelid, cheeks, and neck; immunodeﬁciency; and death in the second decade of life. A high frequency of structural rearrangements of chromosomes 7 and 14 is the cyto- genetic observation with this disease. Figure 2-4 (top) shows the appearance of telangiectasia of the bulbar conjunctiva. Clinical features include: onset of colorectal cancer at a young age, high fre- quency of carcinomas proximal to the splenic ﬂexure, multiple synchronous or metachronous colorectal cancers, and presence of extracolonic cancers (e. Meiosis is a specialized process of cell division (contrasted with mitosis which occurs in somatic cells; see Chapter 10: Cell Cycle) that occurs only in the production of the gametes (i. In female meiosis, each chromosome has a homologous partner whereby the two X chromosomes synapse and crossover just like the other pairs of homol- ogous chromosomes. In male meiosis, there is a problem because the X and Y chromosomes are very different. The pair- ing of the X and Y chromosomes is an end-to-end fashion (rather than along the whole length as for all the other chromosomes) which is made possible by a 2. Crossover introduces one level of genetic variability among the gametes and occurs by a process called general recombination. Alignment refers to the condition whereby the 46 homologous dupli- cated chromosomes align at the metaphase plate. Disjunction refers to the separation of the 46 maternal and paternal homolo- gous duplicated chromosomes from each other into separate secondary game- tocytes (Note: the centromeres do not split). However, the choice of which maternal or paternal homologous duplicated chromosomes enters the secondary gametocyte is a random distribution. It is important to understand that both the “single chromosome” state and “duplicated chromosome” state will be counted as one chromosome 18. The “duplicated chromosome” is often referred to as consisting of two sister chromatids (chromated 1 and chromatid 2). Only one pair of homologous chromosomes is shown (white maternal origin and black paternal origin). There are 2 possible ways the maternal and paternal homologous duplicated chromosomes can be combined. This random distribution of maternal and paternal homologous duplicated chromosomes introduces another level of genetic variability among the gametes. Cell division: two secondary gametocytes (23 duplicated chromosomes, 2 N) are formed. Disjunction: 23 duplicated chromosomes separate to form 23 single chromosomes when the centromeres split. An important example of general recombination occurs during crossover when 2 homologous chromosomes pair during the formation of the gametes. The human nuclear genome consists of 24 different chromosomes (22 autosomes; X and Y sex chromosomes). The fact that the 30,000 genes make up only 2% of the human nuclear genome means ● Figure 4-1 Pie chart indicating the or- ganization of the human nuclear genome. To fully understand how heritable traits (both normal and disease related) are passed down, it is important to understand three aspects of the human nuclear genome which include the following: 1. For decades, protein-coding genes were enshrined as the sole repository of heritable traits. A mutation in a protein-coding gene caused the for- mation of an abnormal protein and hence an altered trait or disease. Exons (expression sequences) are coding regions of a gene with an average size of 200 bp. Introns (intervening sequences) are noncoding regions of a gene with a huge variation in size. A classic gene family is a group of genes that exhibit a high degree of sequence homology over most of the gene length. A gene superfamily is a group of genes that exhibit a low degree of sequence homology over most of the gene length. Examples of gene superfamilies include the immunoglobulin superfamily, globin superfamily, and the G-protein receptor super- family. Genes can be organized as a tandem repeated array with close cluster- ing (where the genes are controlled by a single expression control locus) and com- pound clustering (where related and unrelated genes are clustered) all on a single chromosome. Genes can be organized in a dispersed fashion at two or more differ- ent chromosome locations all on a single chromosome. Genes can be organized in multiple clusters at various chro- mosome locations and on different chromosomes. In humans, there is strong selection pressure to maintain the sequence of im- portant genes. The surplus duplicated genes can diverge rapidly, acquire mutations, and either degenerate into nonfunctional pseudogenes or mutate to produce a functional protein that is evolutionary advantageous. As a result of this process, families of protein-coding genes are frequently characterized by the presence of the following: 1. Processed pseudogenes are typically not expressed as proteins because they lack a promoter sequence. If selection pressure ensures the continued expression of a processed pseudogene, then the processed pseudogene is considered a retrogene. Genomic imprinting is the differential expression of alleles depending on whether the allele is on the paternal chromosome or the maternal chromo- some. When a gene is imprinted, only the allele on the paternal chromosome is expressed, whereas the allele on the maternal chromosome is silenced (or visa versa). During male and female gametogenesis, male and female chromosomes must acquire some sort of imprint that signals the difference between paternal and maternal alleles.

Approximately 50% is excreted in the urine unchanged and thus cheap 10 mg cialis mastercard erectile dysfunction treatment guidelines, captopril plasma clearance is reduced in patients with impaired renal function order cialis with a mastercard erectile dysfunction pills cost. Captopril is used for the treatment of systemic hypertension and congestive heart failure in infants discount cialis 10mg visa young erectile dysfunction treatment, children, and adolescents. It is generally well tolerated, but significant hypotension may occur in volume-depleted patients or in patients with extremely high basal renin activity. When starting captopril therapy for congestive heart failure in neonates and young infants, a low first dose is given and blood pressure should be monitored. Adverse effects include neutropenia and proteinuria, especially in children with underlying renal disease. Less serious reactions include rash, taste impairment, and minor gastrointestinal disturbances. In general, potassium supplements and potassium sparing diuretics should not be administered concomitantly to patients receiving captopril because of the risk of hyperkalemia. Thus, captopril must be used with appropriate caution in adolescent females and should be immediately discontinued if pregnancy occurs. Enalapril and Lisinopril The mechanism of action, hemodynamics, and clinical indications for enalapril and lisinopril are similar to those described above for captopril. The overall incidence of side effects due to enalapril and lisinopril appears to be lower than that reported for captopril. Enalapril and lisinopril have a slower onset of action and longer half-life than captopril and they can be administered once daily which may improve compliance compared to captopril. Enalapril is a prodrug that must be de-esterified to form the active agent, enalaprilat. A liquid formulation of enalapril has recently been made commercially available that avoids the problems in the past that resulted from asking individual pharmacies to compound the tablets into a liquid for infants and young children. A prospective randomized trial of enalapril in infants with a single ventricle did not show any difference in somatic growth, ventricular function, or heart failure severity between enalapril and placebo (83). A combination of valsartan and sacubitril (a neprilysin inhibitor) was shown to be of overwhelming benefit in a large heart failure trial in adults (85). This effect has been shown experimentally to be beneficial in animal models of muscular dystrophy and connective tissue disorders (86,87). However, the rate of change in aortic root dilation was not different for losartan compared with atenolol in a study of children and young adults with Marfan syndrome (88). Aldosterone Receptor Antagonists Activation of the renin-angiotensin system with increased synthesis of aldosterone is a hallmark of the heart failure syndrome. Aldosterone plays an important role in promoting the abnormal collagen production and interstitial fibrosis that occurs in chronic heart failure. An escape of aldosterone production in adult patients is associated with sodium retention, potassium and magnesium loss, excessive myocardial collagen production, ventricular hypertrophy, myocardial norepinephrine release, endothelial dysfunction, and a decrease in serum high-density lipoprotein cholesterol. Administration of aldosterone antagonists, such as spironolactone or eplerenone, to adult patients with heart failure treated with conventional therapy results in increased diuresis and symptomatic improvement (84,89). Spironolactone has been used for years as a potassium-sparing diuretic in infants and children with heart failure, but it has not been extensively studied in this patient population. Whether additional benefit is derived from inhibiting the other effects of aldosterone in pediatric patients remains to be determined. Hormones Nesiritide Nesiritide is a recombinant B type natriuretic peptide that has been studied in adults with heart failure. Despite considerable investigation in the adult population, the role and efficacy of nesiritide is controversial. Several studies in children suggest nesiritide may increase urine output and reduce levels of neurohormonal markers of heart failure. Some centers use nesiritide acutely for infants with low cardiac output following cardiac surgery and for infants with severely depressed cardiac function due to cardiomyopathy (58,90,91). Additional studies are needed to determine the safety and efficacy of nesiritide in pediatric patients with heart disease. Thyroxine and Triiodothyronine Thyroid hormone secretion is reduced in critically ill adults and children following cardiac surgery. These changes in thyroid hormone levels are referred to as “nonthyroidal illness syndrome” and generally have not been thought to represent true hypothyroidism. However, this concept is controversial and some authorities suggest that these patients may have acquired true central hypothyroidism as a consequence of their critical illness or surgical procedure. Some centers administer either thyroxine or triiodothyronine in the postoperative period if thyroid stimulating hormone is elevated, circulating thyroid hormone levels are reduced, and the child has evidence of low cardiac output (92). However, relatively little published information exists regarding the safety, efficacy, and long-term effects of thyroid hormone administration to children in the early post-cardiac surgery period. Additional studies are required to determine if thyroid hormone therapy has a beneficial role in this setting. Vasopressin Vasopressin is a potent vasoconstrictor that acts directly on the vasculature via V1 receptors and indirectly by potentiating the vasoconstrictor effects of catecholamines. Cardiopulmonary bypass produces a systemic inflammatory response that can result in low cardiac output and vasodilatory shock. The first line of therapy in this setting is infusion of catecholamines such as dopamine or norepinephrine. However, shock persists in some infants and children despite maximal supportive therapy. This clinical syndrome mimics that seen in patients with septic shock, which has been associated with depressed levels of vasopressin in adults and children. In contrast to catecholamines, the responses to vasopressin are preserved in the presence of acidosis or hypoxia. Based on results from studies demonstrating a beneficial effect of vasopressin infusion in patients with vasodilatory septic shock, several investigators have administered vasopressin to infants with vasodilatory shock following cardiopulmonary bypass (93,94). In general, the reported results are favorable and it appears that vasopressin can be an effective adjunct to more conventional therapy in this setting. However, additional studies are required to more fully define the indications, safety, and efficacy of vasopressin treatment in children with heart disease. Furthermore, individual drugs differ with regard to the degree of important ancillary properties such as α-adrenergic receptor blockade, antioxidant activity, and intrinsic sympathomimetic activity (95,96). Because of these important differences, the various β-blockers are not interchangeable. Published experience in pediatric patients is limited and therapy for children is derived from adult experiences. These drugs are also used in older children and adolescents, but in these older age groups, drugs such as metoprolol, atenolol, and carvedilol are also used. Propranolol Propranolol was the first commercially available β-adrenergic blocker in the United States.